1. Field of the Invention
The present invention relates to a photo reflector configured to detect an object by a light-emitting element emitting light toward the object, and a light-receiving element receiving the reflected light after the light being reflected on the detected object and converting the reflected light into a photocurrent in the light-receiving element.
2. Description of the Related Art
A conventional photo reflector of this kind is shown in FIGS. 8 and 9. The conventional photo reflector 16 as shown in FIGS. 8 and 9 includes a circuit board 20 provided with electrode patterns 18, a light-emitting element 22 and a light-receiving element 24 which are electrically connected to the electrode patterns 18 of the circuit board 20, respectively, and a light-shielding frame 26 which is provided on the circuit board 20 to surround the light-emitting element 22 and the light-receiving element 24 and has an partition wall 26b to partition and optically shield the light-emitting element 22 and the light-receiving element 24 (for reference, see Japanese Patent Laid Open No. 2001-156325).
In the photo reflector 16, the light-emitting element 22 and the light-receiving element 24 are positioned to be close to each other in one side with the partition wall 26b disposed between the light-emitting element 22 and the light-receiving element 24. The light-shielding frame 26 shields unnecessary light and the partition wall 26b prevents direct light of the light-emitting element 22 from entering the light-receiving element 24.
However, the photo reflector 16 having the aforementioned structure has variations in light-emission intensity of the light-emitting element 22 and light-receiving sensitivity of the light-receiving element 24. Consequently, a photocurrent value determined by a combination characteristic (sensor sensitivity characteristic) of light-emitting element and light-receiving element in the photo reflector 16 tends to have a significant variation in which the maximum value may be about three-time value of the minimum value. This variation not only depends on the inherent characteristics of the light-emitting element 22 or the light-receiving element 24, but may also occur with each lot in a manufacturing step.
When there is this kind of variation in the photocurrent value, it is feared a fear that products cannot be stably provided due to a large number of defective products occurring in the pre-shipping inspection.
In addition, the conventional photo reflector is produced after carrying out design of such factors as selection of the light-emitting element or light-receiving element, or shape or size of the light-shielding wall, upon previous consideration of characteristics such a photocurrent or the like. However, until a final product is once manufactured, it is not possible to determine whether the product satisfies the characteristics as designed. Therefore, if a product does not satisfy the conditions as designed in the final inspection, it is not possible to ship it as a product, and the process yield of the products is reduced.